scholarly journals Weak deflection angle of black-bounce traversable wormholes usingGauss–Bonnet theorem in the dark matter medium

2020 ◽  
Vol 44 (5) ◽  
pp. 465-471
Author(s):  
ALİ ÖVGÜN
Keyword(s):  
Dark Matter ◽  
Deflection Angle ◽  
Light Bending ◽  
Traversable Wormholes ◽  
Bonnet Theorem

In this paper, we first use the optical metrics of black-bounce traversable wormholes to calculate the Gaussiancurvature. Then we use the Gauss–Bonnet theorem to obtain the weak deflection angle of light from the black-bouncetraversable wormholes. We investigate the effect of dark matter medium on weak deflection angle using the Gauss–Bonnet theorem. We show how weak deflection angle of wormhole is affected by the bounce parametera. Using theGauss–Bonnet theorem for calculating weak deflection angle shows us that light bending can be thought as a global andtopological effect.

scholarly journals Weak Deflection Angle of Black-bounce Traversable Wormholes Using Gauss-Bonnet Theorem in the Dark Matter Medium

2020 ◽  
Author(s):  
Ali Övgün
Keyword(s):  
Dark Matter ◽  
Gaussian Curvature ◽  
Deflection Angle ◽  
Light Bending ◽  
Traversable Wormholes ◽  
Topological Effect ◽  
Bonnet Theorem

In this paper, first we use the optical metrics of black-bounce traversable wormholes to calculate the Gaussian curvature. Then we use the Gauss-Bonnet theorem to obtain the weak deflection angle of light from the black-bounce traversable wormholes. Then we investigate the effect of dark matter medium on weak deflection angle using the Gauss-Bonnet theorem. We show how weak deflection angle of wormhole is affected by the bounce parameter $a$. Using the Gauss-bonnet theorem for calculating weak deflection angle shows us that light bending can be thought as a global and topological effect.

scholarly journals Effect of the Dilaton Field on Deflection Angle of Massive Photons by Black Holes in Einstein-Maxwell-Dilaton-Axion Theory

2019 ◽  
Author(s):  
Wajiha Javed ◽  
Rimsha Babar ◽  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Dark Matter ◽  
Deflection Angle ◽  
Weak Field ◽  
Dilaton Field ◽  
Plasma Medium ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
Massive Photons

In this paper, we argue that one can calculate the weak deflection angle in the background of Einstein-Maxwell-Dilaton-Axion black hole using the Gauss-Bonnet theorem. To support this, the optical geometry of the black hole with the Gibbons-Werner method are used to obtain the deflection angle of light in the weak field limits. Moreover, we investigate the effect of a plasma medium on deflection of light for a given black hole. Because of dilaton and axion are one of the candidate of the dark matter, it can give us a hint on observation of dark matter which is supported the black hole. Hence we demonstrate the observational viability via showing the effect of the dark matter on the weak deflection angle.

scholarly journals Deflection Angle of Photons through Dark Matter by Black Holes and Wormholes Using Gauss–Bonnet Theorem

Universe ◽  
2019 ◽  
Vol 5 (5) ◽  
pp. 115 ◽  
Author(s):  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Dark Matter ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Compact Objects ◽  
Asymptotically Flat ◽  
Optical Geometry ◽  
Topological Effect ◽  
Bonnet Theorem ◽  
Fish Eye

In this research, we used the Gibbons–Werner method (Gauss–Bonnet theorem) on the optical geometry of a black hole and wormhole, extending the calculation of weak gravitational lensing within the Maxwell’s fish eye-like profile and dark-matter medium. The angle is seen as a partially topological effect, and the Gibbons–Werner method can be used on any asymptotically flat Riemannian optical geometry of compact objects in a dark-matter medium.

scholarly journals Weak Deflection Angle of some Classes of non-linear Electrodynamics Black Holes via Gauss-Bonnet Theorem

2020 ◽  
Author(s):  
Hasan El Moumni ◽  
Karima Masmar ◽  
Ali Övgün
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Weak Field ◽  
Leading Order ◽  
Plasma Medium ◽  
Non Linear ◽  
The Deflection Angle ◽  
Bonnet Theorem

In this paper, we study the gravitational lensing by some black hole classes within the non-linear electrodynamics in weak field limits. First, we calculate an optical geometry of the non-linear electrodynamics black hole then we use the Gauss-Bonnet theorem for finding deflection angle in weak field limits. The effect of non-linear electrodynamics on the deflection angle in leading order terms is studied. Furthermore, we discuss the effects of the plasma medium on the weak deflection angle.

scholarly journals Deflection of light by a rotating black hole surrounded by “quintessence”

2020 ◽  
Vol 35 (26) ◽  
pp. 2050155 ◽  
Author(s):  
Prateek Sharma ◽  
Hemwati Nandan ◽  
Radouane Gannouji ◽  
Rashmi Uniyal ◽  
Amare Abebe
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Deflection Angle ◽  
Energy Condition ◽  
Additional Parameter ◽  
Deviation Angle ◽  
Extremal Case ◽  
Rotating Black Hole ◽  
State Formula ◽  
Kerr Space

We present a detailed analysis of a rotating black hole surrounded by “quintessence.” This solution represents a fluid with a constant equation of state, [Formula: see text], which can for example describe an effective warm dark matter fluid around a black hole. We clarify the conditions for the existence of such a solution and study its structure by analyzing the existence of horizons as well as the extremal case. We show that the deflection angle produced by the black hole depends on the parameters [Formula: see text] which need to obey the condition [Formula: see text] because of the weak energy condition, where [Formula: see text] is an additional parameter describing the hair of the black hole. In this context, we found that for [Formula: see text] (consistent with warm dark matter) and [Formula: see text], the deviation angle is larger than that in the Kerr space–time for direct and retrograde orbits. We also derive an exact solution in the case of [Formula: see text].

scholarly journals Possible formation of wormholes from dark matter in an isothermal galactic halo and void

2019 ◽  
Vol 34 (23) ◽  
pp. 1950188
Author(s):  
Nayan Sarkar ◽  
Susmita Sarkar ◽  
Farook Rahaman ◽  
P. K. F. Kuhfittig ◽  
G. S. Khadekar
Keyword(s):  
Dark Matter ◽  
Galactic Halo ◽  
Energy Condition ◽  
Null Energy Condition ◽  
Galactic Rotation ◽  
Einstein Field Equations ◽  
Field Equations ◽  
Rotation Curves ◽  
Galactic Rotation Curves ◽  
Traversable Wormholes

It is well-known that traversable wormholes are valid solutions of the Einstein field equations, but these structures can only be maintained by violating the null energy condition. In this paper, we have obtained such wormhole solutions in an isothermal galactic halo, as well as in a void. We have shown that the null energy condition is violated, with the help of a suitable redshift function obtained from flat galactic rotation curves.

scholarly journals Traversable wormholes supported by GUP corrected Casimir energy

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Kimet Jusufi ◽  
Phongpichit Channuie ◽  
Mubasher Jamil
Keyword(s):  
Deflection Angle ◽  
Equations Of State ◽  
Generalized Uncertainty Principle ◽  
Casimir Energy ◽  
Energy Conditions ◽  
Strong Condition ◽  
Asymptotically Flat ◽  
Wormhole Throat ◽  
Classical Energy ◽  
Traversable Wormholes

Abstract In this paper, we investigate the effect of the Generalized Uncertainty Principle (GUP) in the Casimir wormhole spacetime recently proposed by Garattini (Eur Phys J C 79: 951, 2019). In particular, we consider three types of GUP relations, firstly the Kempf, Mangano and Mann (KMM) model, secondly the Detournay, Gabriel and Spindel (DGS) model, and finally the so-called type II model for the GUP principle. To this end, we consider three specific models of the redshift function along with two different equations of state (EoS), given by $${\mathcal {P}}_r(r)=\omega _r(r) \rho (r)$$Pr(r)=ωr(r)ρ(r) and $${\mathcal {P}}_t(r)=\omega _t (r){\mathcal {P}}_r(r)$$Pt(r)=ωt(r)Pr(r) and obtain a class of asymptotically flat wormhole solutions supported by Casimir energy under the effect of GUP. Furthermore we check the null, weak, and strong condition at the wormhole throat with a radius $$r_0$$r0, and we show that in general the classical energy conditions are violated by some arbitrary quantity at the wormhole throat. Importantly, we examine the wormhole geometry with semiclassical corrections via embedding diagrams. We also consider the ADM mass of the wormhole, the volume-integral quantifier to calculate the amount of the exotic matter near the wormhole throat, and the deflection angle of light.

scholarly journals Deflection angle of light by wormholes using the Gauss–Bonnet theorem

2017 ◽  
Vol 14 (12) ◽  
pp. 1750179 ◽  
Author(s):  
Kimet Jusufi
Keyword(s):  
Deflection Angle ◽  
Weak Limit ◽  
Space Time ◽  
Geometrical Method ◽  
Optical Geometry ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
Limit Approximation

In this paper, we have investigated the deflection angle of light by wormholes using a new geometrical method known as Gibbons–Werner method (GW). In particular, we have calculated the deflection angle of light in the weak limit approximation in two wormhole space–time geometries: Ellis wormhole and Janis–Newman–Winnicour (JNW) wormhole. We have employed the famous Gauss–Bonnet theorem (GBT) to the Ellis wormhole optical geometry and JNW wormhole optical geometry, respectively. By using GBT, we computed the deflection angles in leading orders by these wormholes and our results were compared with the ones in the literature.

scholarly journals Effect of Horndeski Theory on Weak Deflection Angle Using the Gauss-Bonnet Theorem

2021 ◽  
Author(s):  
Ali Övgün ◽  
Yashmitha Kumaran ◽  
Wajiha Javed ◽  
Jameela Abbas
Keyword(s):  
Black Hole ◽  
Gravitational Lensing ◽  
Deflection Angle ◽  
Field Approximation ◽  
Weak Field ◽  
Plasma Medium ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
The Impact ◽  
Do So

The main goal of this paper is to study the weak gravitational lensing by Horndeski black hole in weak field approximation. In order to do so, we exploit the Gibbons-Werner method to the optical geometry of Horndeski black hole and implement the Gauss-Bonnet theorem to accomplish the deflection angle of light in weak field region. Furthermore, we have endeavored to extend the scale of our work by comprising the impact of plasma medium on the deflection angle as properly. Later, the graphical influence of the deflection angle of photon on Horndeski black hole in plasma and non-plasma medium is examined.

scholarly journals Weak Deflection Angle by Casimir Wormhole Using Gauss-Bonnet Theorem and Its Shadow

2020 ◽  
Author(s):  
Wajiha Javed ◽  
Ali Hamza ◽  
Ali Övgün
Keyword(s):  
Event Horizon ◽  
Deflection Angle ◽  
Weak Limit ◽  
Plasma Medium ◽  
Spacetime Geometry ◽  
The Deflection Angle ◽  
Bonnet Theorem ◽  
Limit Approximation ◽  
Optical Metric

Here we calculate the deflection angle of photon by Casimir wormhole in weak limit approximation. First we calculate Gaussian optical curvature with the help of optical spacetime geometry and so we use the Gauss-Bonnet theorem on Gaussian optical metric and find deflection angle of photon by Casimir wormhole. Moreover, we calculate the photon's deflection angle in the presence of plasma medium and we also see the graphical nature of deflection angle in both cases. After calculating the deflection angle of Casimir wormhole. Now, we move towards the shadow of Casimir wormhole. After the observations of Event Horizon Telescope, the study of shadow become very important so that we plot the shapes of shadow of Casimir wormhole, and we calculate the photon geodesic around the Casimir wormhole.

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